Motor arc-lamp.



C. KRAMER.-

MOTOR ARC LAMP.

APPLICATION FILED AUG-25, 1915.

- Patented July 17, 1917.

lnvehtor Christian Kramer 9mm HiS A CLOTHeq 'IUNI ED STATES PATENT OFFICE.

CHRISTIAN KRAMER; OF BERLIN, GERMANY, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

moron ARC-LAMP.

Specification of Letters Patent.

Patented July 17, 1917.

Application filed August 25, 1915. Serial No. 47,373.

To all whom it may concern: 7

Be it known that I, CHRISTIAN KRAMER, a subject of the King of Bavaria, residing at Berlin, Germany, have invented certain new and useful Im rovements in Motor Arc-Lamps, of whic the following is a specification.

My invention has reference to improvements in the method of and apparatus for regulating motor arc lamps; that is to say, arc jla-mps in which the electrodes are moved toward and from each other by a reversible electric motor, as is ordinarily the case with are lamps-for searchlights.""The object of my invention is to provide a method and the meanswhetebythe motorjs made to run in either direction fast or slow, according to the demands of regulation under Varying potentials when a constant-current siipply is provided.

When the arc is in the neighborhood of its desired normal lengthfor potential) the regulation'of' the electrodes for variations of length of arc should be'slow, so that onftheone hand no overfeedi'ng and on the other. hand no separation. of the electrodes in encess of theprequirement occur. If, however,- the arcshould become excessively long,

then a rapid approach of theelectrodes is demanded, and if for some reason or otherthe arc shouldbreak, the electrodes should be approached with-still greater rapidity, so as to reestablish the are as quickly as' possible; also, when thegelectrodes are in contact and the current is started, the elec.-

trodes should be separated promptly. All these conditions are provided for by my method of operation by the use of a differential magnet actuating an armature which in turn controls-a series. of freely movable, pressure contacts on either side of the armature' and which contacts control resistances in the motor circuit in such away that-the direction of rotation of the motor is controlled and its speed is regulated in accordance with thedemands aboveindicated.

ln-the accompanying drawing, Figure 1 a diagram of an apparatus by means of which my invention may be practised, and Fig. 2 is an elevation of a detailof the apparatus. y

In this drawing (Fig. 1), 1 represents a constant current generator; 2 and 3 the -main line; 4 and 5 the electrodes of the lamp, 4 being the anode and 5 the cathode.

A- horseshoe electromagnet 6 has a series 11 and 12 held in a certain position other than the one shown in the drawing, as will be explained farther on. vOn either side of the contact 11 is a series of other contacts; namely,'contacts 12, 13, 14, and 15 on the left hand side, and contacts 16, 17,

- 18, and 19 on the right'handside: The end contacts .15. and 19'are'supported upon upstandingrigid arms .20, .21 respectively, while the intermediate contacts are supported by leaf springs 22 in such manner that all these contacts are free of each-other when the armature 9 is in its middle position; they are in a-row so arranged that when the contact llmoves toward the left it first strikes the contact 12; and upon further movement to the left this contact 12 comes into engagement with the contact 13, thencontact l3'comes into engagement with. contact 14, and finally contact 14 comes into engagement with contact 15. Similarly, when contact 11 moves toward the right it engages contact 16, then contact 16 engages conta'ctlf, then contact 17 engages contact 18',"and finally contact 18 engages contact 19.

An electric motor is provided whose armature 23 is geared with the electrodes in such a manner as to propel them in one direction or the other, according to the direction of its rotation. This is a common arrangement "in lamps of this character, and for this reason and'for the sake of simplicity of illustration the gearing is not shown. The field magnet coil of the motor is indicated at 24. The motor armature 23 forms the bridge wire of a Wheatstone bridge of which the resistances 25 and 26 form the two sides of onebran'ch and the. resistances 27 and 28 plus the resistance of the field magnet; wind- 24' forms 1 the: two sides of the other branch of theNVheatstonebridge, the whole 7 Wheatstone bridge be ng. in a shunt 29,30

around the generatonl, or what is the same thing, aroundf'theelectrodes of the lamp.

One branckof the..Wheats tone bridge may be traced from the plus pole of the generator 1, to point 31, conductor 29, point 32, re-- sistance 25, point 33, resistance 26, point 34, conductor 35, point 36, conductor 30, point 37, to the minus pole of the generator. The other branch of the Wheatstone bridge is from the plus terminal of the generator to point 31, by conductor 29, point 38, conductor 39, point 40, resistance 27, point 41, resistance 28, conductor 42, field coil 24, point 36, conductor 30, point 37, back to the minus terminal of the generator. The bridge wire including the armature terminates on one side at the point 33, between theresistances 2,5 and 26, and on the other side at the point 41, between resistances 27 and 28 plus field magnet coil 24. The resistances constituting the sides of the Wheatstone balance may either'all be equal or may be proportioned in a manner well understood by those skilled in the art. In either case,'when all the resistances enumerated are in the circuit, the difference of potential between the armature terminals is zero and no current passes through the armature. This condition is brought about by suitable adjustment of the tension of the length of the arc.

contact 11 toward the left until it bears.

upon the contact 12, whereby the portion of the resistance 25 which extends to the left of the point 47 is short circuited. This disturbs the balance of the Wheatstone bridge and the motor armaturereceives current in the direction of the arrow (2, as can be readily traced; thus: from the plus pole of the generator to' point 31, conductor 29, point 32,'the left endportion of resistance 25, leaf spring 22. to contacts 12and 11, flexible conductor 45, point 33, to armature 23 in the direction of arrow (1, through armature 23, to point 41, resistance 28, conduetor 42, field coil 24, point 36, conductor 30, point 37 back to the minus pole of the generator. thatevent is suchas to operate to approa the electrodes to reestablish the norma The movement of the armature is under these circumstances slow, because the balance of the Wheatstone bridge has only been slightly disturbed by the cutting out of a portion of the resistance 25. If, however, the arc becomes still springs 11 and 11 which is so made that when the arc has the desired normal length (ordinarily at a voltage .of 70 volts), the

armature 9 is in the position shown in the drawing, with the contact 11 free between the contacts 12 and 16.

From the point 41 branches a resistance 43 which is connected with the leaf spring 22 that carries the contact 14 by a conductor 44, and the point 33 between the two resistances 25 and 26 is connected with the contact 11 by a flexible conductor 45. The point 36 where the shunt wire 30 meets one terminal of the field coil 24 is connected by a conductor 46 with the rigid standard 20 longer than before, the magnetizing effect of the shunt coil predominates still more and the armature 9 moves clockwise to a V greater angle, and the contact 11 eventually pushes the contact'120nto1the c ontact 13, whereby the whole of the resistance 25"i short circuited, the balance of the Wheatstone bridge is disturbed to a greater extent and the IIIOtOI armature receives more C111:

rent than before, but still in the same direc- 7 tion, and, therefore, rotates faster to apwhich carries the contact 15. Similarly, thep0i11t41 is connected with the rigid standard 21 which carries the contact '19. The point 32 is connected with the leaf spring 22 which carries the contact 13; some intermediate point 47 of the resistance 25 is connected with the leaf spring 22 which carries the contact 12; some intermediate point 48 of the resistance 26 is connected with the leaf spring 22 which carries the contact 16; the point 34 is connected with the leaf spring 22 which carriesthe contact 17; and the point 40 is connected with the leaf spring 22 which carries the contact 18.

proach the electrodes at a quicker rate than before. If by any accident the arc should become excessively long, or if it should break altogether, the potential difference between the electrodes would become very great, the magnetizing effect of the shunt coil 8 would predominate still more, and the armature 9 would moveclockwiseto a still greater angle and would shift the contact 11 to tht left to such an extent that the whole series omtacts onLhis ide would come into contact. It will be noticed "that the opposing ends of the contacts 13, 14 areshaded, and this is to indicate that these ends are made of insulating material. Now,

' by the movement of the contact 11 to the left of the carbons, the arc lengthens and thereby the potential rises, the magnetizing effect of the shunt coil 8 is predom natlng and the armature'Q turns clockwise and moves the to the extent of making each of the left hand contacts to bear .upon the next succeeding one so that contact 14 bears upon contact 15,-

the resistance 43 short circuits or diverts a part of the current from the field coil 24, thereby weakens the field and causes the motor armature to speed up still more than before, so that the electrodes are now moved very rapidly toward contact. The shunting of the field coil by contacts 14, 15 can be readily seen by tracing the current through the field before'and after the contacts 14, 15. have touched. Before they have touched the motor current passing through the armature in the direction of the arrow 0. passes'on through resistance 28, conductor 42, through field coil 24 and by conductor to the generator; whereas after the contacts 14 and 15 have touched a part of the current through the. field still passes as before, but a portion of the currentis now diverted at the point -21 by resistance 43, conductor 44, leaf spring 22 which carries contact 14, contact 15, rigid arm 20, conductor 46, by point 36 and conductor 30 to the generator.

It will be seen from the foregoing that when the arc grows longer than is desired the motor operates first slowly and when are potential may be one-half and more of the potential of the arc of normal length. Thus, if the normal are potential is seventy volts, the restarted are, which appears when the hot electrodes are approached, may have a potential as high as forty volts. Under these circumstances the magnetizing effect of the series coil 7 slightly predominates, the

' armature 9 swings counterclockwise and the while the generator is at work the difierence arm ill-moves toward the right until the contact 11 bears upon the contact 16. The effect of this is that the left hand portion of the resistance 48 is short circuited, the balance of the Wheatstone bridge is slightly disturbed so that current now flows through the armature in the direction of the arrow 6,

' while through the-field coil it still flows-in the same direction as before. This can be traced as follows: from the plu s pole of the generator to" the point 31, conductor 29,

.point 38, conductor 39, point 40, resistance 27, to point 41 where the current divides, one.

portion going to the armature in the direc tion of the arrow 6 to point 33, flexible conductor 45, contacts 11 and 16,1eafspring 22, point 48, the right hand part of'resistance 26, conductor 35, poiiitT-36, conductor 30, point 37, to the minus'poleof the generator; the other part of the current proceeding 55; from point 41, passes throughresistance 28,

conductor 42, field coil 24, conductor. 30, point 37, to the pole of the generator. In this manner'the rotation of the 'motor armature is reversed so that it will act to slowly further separate the electrodes the normal length of the arc is reache r .which the regulation proceeds as before described. 7 v, -I f the electrodes are in.actual' contact of potential between them is very small and the magnetizin g etlect of the series coil strongly predominates. The armature 9, thereftre, swings violently counterclockwise so that the contact 11 brings all the successive contacts on the right together. The effect of this is that all of the resistances 26, 27 are short circuited and the motor is speeded up to separate the electrodes rapidly until the are has attained its normal length. The course of the current at this action can be traced easily if notice is taken of the fact that the opposing surfaces of contacts 18 and 17 are made'of insulating material, as is indicated by heavy shading.

It will be understood, without further explanation, that instead of dividing the resistances 25 and 26 into two parts only, they might be divided intothree or more parts by correspondingly increasing the number of contacts and leaf springs. It will also be understood that when the electrodes are being separated for striking the are, it is quite practicable, in addition to short circuiting the resistances 26 and 21, also to short circuit the resistance 28 by the resistance 48, or otherwise, and thereby weaken the field'current, thus speeding up the motor still more. But this has been found to be unnecessary.

I have hereinbeforc pointed out that the tension of the springs 11, 11 is so adjusted as to bring the contact ll midway between the contacts 12 and 16 when the arc has the desired normal length. I Of course, the length of the arc itself is not-measured, but

. the voltage at the-arc is measured, which' voltage corresponds to a particular length of are. In practice it has been found that the normal voltage which may with advantage be maintained varies with the current strength employed. Thus, for a current of 160 ampe'res the normal voltage should be about volts; with 200 amperes the normal voltage should be about volts; and with 120 amperes the best voltage would be about 60'volts. Now, whatever normal "voltage is determined upon for any given constant current, the tension of the springs 11' and 11 must be so adjusted as tobringthe contact 11 midway between the contacts- 12 and 16 when that normal voltage esistsifln consequence of this adjustment, when there is no current on the lamp, at which time the carbons arel out of contact, the spring feed the electrodes together until they touch, whereupon they are separated, as hereinbefore described, for anew start of. the are. i

Whenever the contact 11 is in the central position, the motor armature circuit is closed upon itself, through the two branches of the Wheatstone bridge, and if at that instant the armature has a tendency to rotate, it acts as a geneFator, that is to say, as a brake upon itself and is promptly stopped. 1

With the construction here shown the leaf springs 22 on the left hand side of the contact 11 should be prevented from vibrating toward the right hand side beyond the positions indicated in the drawing; and, similarly, the leaf springs 22 on the right hand side of the contact 11 should be prevented from vibrating to the left beyond their po- 'sitions shown in thedrawing, since otherwise accidental and undesirable contacts might occur which would greatly disturb the regulation. In order to prevent such vibration the construction of the leaf spring contact supports is as shown in Fig. 2.

Refefring to Fig. 2, it will be seen that the-leaf spring 22 carries at its free end a hollow metal piece 49 in which the contact proper is mounted. This contact may be either a piece'of carbon projecting at both ends beyond the metal piece, it the contact is'to be conducting on both ends, such as contacts 12 and 16', or it may be a piece of" carbon with some insulation at one end, if it is to be conducting at one end only,

such as the contacts 13,14, 18' and17; or

the conducting portion may be of metal. In'Fig. 2 I have shown the latter construction, in which the contact is formed of a ss metal block 49 which is bored-out at one end and has a piece of insulating material '50 inserted in and projecting beyond the cavity. On one side of the leaf spring 22, secured to its lower end is a rigid arm 22 which extends upward throughout the length of the spring, diverging upwardly from the spring and at its upper end curving toward the spring. The spring'22 is biased to hear at or near its upper end, just underneath the block 49 against the .upper end-of the rigid arm 22. It will be seen that with this construction the leaf spring, and, therefore, the contact which it carries can only vibrate on one side of the rigid arm,22,in the case shown on the left. This effectually prevents accidental contacts which might occur if the leaf springs were free to vibrate on either side of their normal positions. As a result of the use of the contacts mounted as shown in Fig. 2,

the movement of the armature 9 and of the contact 11, is frictionless, ,which is a feature of considerable value.

What I claim as new and desire to secure by'LettersPatent of the United States, is

1. The methodl of electric arc lamp regulation, which consists in causing the electrodes to approach each other and to recede from each other, in accordance with the variation of the are potential above and beitself.

low its normal value, and at a rate corresponding to the magnitude of the variation 1n such manner as to still have considerable speeding the movements of the electrodes in accordance with the amount of variation of potential, from the normal and braking the motor by converting it into a generator closed upon itself when the are potential becomes normal. 7

3. The method of electric arc lamp regulationfvvhich consists in actuating an electric motor to approach and separate the electrodes in accordance with the rise and drop, respectively, of the are potential with reference toa predetermined normal value, speeding the movements of the electrodes in accordance with the amount of variation of potential from the normal in such manner as to still have considerable speed when the arc potential becomes normal, and braking the motor at that phase of the operation by converting it into a generator closed upon 4:. An electric arc lamp comprising a pair of electrodes, an electrode propelling electric motor whose armature is in the bridge wire and whose field winding is in one of the sides of a Wheatstone bridge, said Wheatstone bridge being in a shunt around the arc,means extraneous to the are for balanctential is normal and for 'unbalancing the Wheatstone bridge when the are potential rises or drops.

5. An electric arc lamp comprising a pairg,

' of electrodes, an electrode propelling electric motor whose armature is in the bridge wire and whose field winding is in one-of the sides of a Wheatstone bridge, said Wheatstone bridge being in a shunt around the are,

means for balancing the Wheatstone bridge "when the are potential is normal and for unbalancing the Wheatstone bridge when the are potential rises or drops and corresponding to the. amount of suchrise and drop.

6. An electric arc lamp comprising a pair of electrodes, an electrode propelling electric motor whose armature is in the bridge wire and whose field winding is in one of the sides of a Wheatstone bridge, said Wheatstone bridge being in a shunt around the arc,resistances in the sides of the Wheatstone bridge for balancing the latter when w the are potential is normal, an electromagnet difierentially energized by a series and a shunt'coll, an armature for the electromagiat" net, and means controlled'by thearmature for varying the resistances to unbalance the Wheatstone bridge approximately in the measure as the are potential rises or drops.

7. An electricarc' lam comprising a pair of electrodes, an electro e propelling motor whose armature is in the bridge Wire and whose field winding is in one of the sides of 'a Wheatstone bridge, said Wheatstone bridge being in a shunt around the arc, resistances in the sides of the'Wheat'stone bridge for balancing the latter when the arc potential is normal, an electromagnet differentially energized by a series and shunt coil, a contact carrying armature for the electromag' In witness whereo I have hereunto set 25 my hand this 12th day of July,.1915.

CHRISTIAN 

